SHIP negatively regulates IgE+ antigen-induced IL-6 production in mast cells by inhibiting NF-κB activity

J Kalesnikoff, N Baur, M Leitges… - The Journal of …, 2002 - journals.aai.org
J Kalesnikoff, N Baur, M Leitges, MR Hughes, JE Damen, M Huber, G Krystal
The Journal of Immunology, 2002journals.aai.org
We demonstrate in this study that IgE+ Ag-induced proinflammatory cytokine production is
substantially higher in Src homology-2-containing inositol 5′-phosphatase (SHIP)−/− than
in SHIP+/+ bone marrow-derived mast cells (BMMCs). Focusing on IL-6, we found that the
repression of IL-6 mRNA and protein production in SHIP+/+ BMMCs requires the enzymatic
activity of SHIP, because SHIP−/− BMMCs expressing wild-type, but not phosphatase-
deficient (D675G), SHIP revert the IgE+ Ag-induced increase in IL-6 mRNA and protein …
Abstract
We demonstrate in this study that IgE+ Ag-induced proinflammatory cytokine production is substantially higher in Src homology-2-containing inositol 5′-phosphatase (SHIP)−/− than in SHIP+/+ bone marrow-derived mast cells (BMMCs). Focusing on IL-6, we found that the repression of IL-6 mRNA and protein production in SHIP+/+ BMMCs requires the enzymatic activity of SHIP, because SHIP−/− BMMCs expressing wild-type, but not phosphatase-deficient (D675G), SHIP revert the IgE+ Ag-induced increase in IL-6 mRNA and protein down to levels seen in SHIP+/+ BMMCs. Comparing the activation of various signaling pathways to determine which ones might be responsible for the elevated IL-6 production in SHIP−/− BMMCs, we found the phosphatidylinositol 3-kinase/protein kinase B (PKB), extracellular signal-related kinase (Erk), p38, c-Jun N-terminal kinase, and protein kinase C (PKC) pathways are all elevated in IgE+ Ag-induced SHIP−/− cells. Moreover, inhibitor studies suggested that all these pathways play an essential role in IL-6 production. Looking downstream, we found that IgE+ Ag-induced IL-6 production is dependent on the activity of NF-κB and that IκB phosphorylation/degradation and NF-κB translocation, DNA binding and transactivation are much higher in SHIP−/− BMMCs. Interestingly, using various pathway inhibitors, it appears that the phosphatidylinositol 3-kinase/PKB and PKC pathways elevate IL-6 mRNA synthesis, at least in part, by enhancing the phosphorylation of IκB and NF-κB DNA binding while the Erk and p38 pathways enhance IL-6 mRNA synthesis by increasing the transactivation potential of NF-κB. Taken together, our data are consistent with a model in which SHIP negatively regulates NF-κB activity and IL-6 synthesis by reducing IgE+ Ag-induced phosphatidylinositol-3, 4, 5-trisphosphate levels and thus PKB, PKC, Erk, and p38 activation.
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